As a background technique of this technical field, the fuel injection valve described in Japanese Laid-open Patent Application 2011-144731 (Patent Document-1) is known. The known fuel injection valve of the publication is equipped with a needle valve that is connected to a movable core (movable iron core) by press fitting and welding (paragraph 0047). For communicating an internal space of the movable iron core with an internal space of the needle valve, a connected part between the movable iron core and the needled valve is formed with an inlet opening (paragraph 0044). In a shaft portion of the needle valve, there are formed both a communication hole and another communication hole that are respectively arranged in upstream and downstream sides with respect to a flow direction of fuel. The upstream-side communication hole comprises a plurality of circular openings that are formed near an end (upstream side end portion) of the shaft portion that is connected to the movable iron core. The downstream-side communication hole comprises a plurality of oval openings that are formed near an end (upstream side end portion) of the shaft portion that is sealed. The upstream-side communication hole and the downstream-side communication hole are so constructed that the interior of the shaft portion is communicated with an interior space that is formed in a nozzle holder and a nozzle body through which the needled valve is received (paragraph 0044). With this construction, fuel led into the fuel injection valve from a fuel inlet portion (fuel supply opening) is led into an inner circumference side of the movable iron core, the inlet opening and then into an inner circumference side of the shaft portion of the needle valve. The fuel led into the shaft portion is led into the space formed between the needle valve and a unit of the nozzle holder and nozzle body after passing through the upstream-side communication hole and the downstream-side communication hole (paragraph 0056).
In the fuel injection valve disclosed in Patent Document-1, the shaft portion is constructed of a cylindrical member and fuel in the shaft portion is led into the outside through the communication holes. In this case, however, the interior of the shaft portion tends to generate a dead fuel flow region (stagnation) and a part where the fuel flow speed is lowered.
In fuel injection valves, for dealing with a case in which a foreign thing is accidently mixed into a fuel flow passage of the fuel injection valve during the production process, the fuel injection valves produced are subjected to a running-in operation for discharging the foreign thing to the outside. Thus, if the above-mentioned dead fuel flow region (stagnation) and the lowered fuel speed region are present, discharging the foreign thing to the outside takes time and thus the running-in operation of the valves has to be carried out for a long time. Production efficiency is lowered as the running-in operation takes a longer time. Furthermore, energy and cleaning liquid consumed by the running-in operation are increased.